1. Field of the Invention
Aspects of the present invention relate to a hydrogen generator and a fuel cell using the same, and more particularly, to a hydrogen generator capable of achieving a high energy density and having a controllable hydrogen generating rate, and a fuel cell using the same.
2. Description of the Related Art
Fuel cells obtain electromotive force by a cell reaction which generates water from hydrogen and oxygen. Fuel cells can operate continuously insofar as fuel and oxidant are continuously supplied to the fuel cell.
A fuel cell is typically formed of an anode, a cathode, and an electrolyte disposed between the anode and the cathode. The anode and the cathode generally include a catalyst which facilitates an oxidation reaction and a reduction reaction which generate electricity. A polymer electrolyte membrane fuel cell (PEMFC), as an example of the fuel cell, is known to have a proton exchange membrane.
The PEMFC supplies hydrogen and oxygen from an external supply source to the fuel cell. Then, once hydrogen flows into the anode side of the fuel cell, oxidation takes place, producing H+ ions and electrons (e−). The electrons (e−) are transported to an external circuit through the anode and returns to the cathode side of the fuel cell. Oxygen flows into the cathode side of the fuel cell, where reduction takes place, producing oxygen atoms with negative charges. Two hydrogen ions each with a positive charge form a bond with a single oxygen atom with negative charges and two electrons which return to the cathode from the external circuit to form water molecules.
Typical supply sources of hydrogen are liquid hydrogen, compressed hydrogen gas, or hydrogen-rich gas from a natural gas reformer. However, it is difficult to guarantee the safety of these hydrogen supply sources due to a danger of hydrogen explosion. In addition, a “volume or weight vs. hydrogen storage capacity” ratio (or storage density) is very low due to a large weight and volume of a container to store the hydrogen and an accompanying apparatus.
As a result of attempts to develop a safe hydrogen supply source with high hydrogen storage density, methods of generating hydrogen using hydrolysis of metal hydrides, such as hydrolysis of sodium boron hydride (NaBH4) are being used. Korean Patent Laid-Open Publication No. 2005-93607 discloses a method of generating hydrogen by contacting a stabilized NaBH4 solution to a hydrogen-generating catalyst. In addition, Japanese Patent Laid-Open Publication No. 2002-80201 discloses a method of generating hydrogen by adding an acidic solution to an alkaline earth metal hydride.